Metal-to-metal seal with soft metal insert

ABSTRACT

An annular metal-to-metal sealing system, for use in wellhead systems and having many other uses, has a metal member defining an annular internal or external sealing surface for which sealing is intended. An annular seal body composed of high strength metal material is positioned in concentric relation with the annular sealing surface and is sufficient flexible to become spring loaded, typically during assembly, for continuous application of a spring force. The annular seal body defines one or more annular seal retainer grooves each having an annular soft metal sealing insert therein, with a portion thereof exposed for sealing engagement with the annular sealing surface. The spring loaded characteristic of the annular seal body applies constant force to maintain the soft metal seal insert in constantly energized sealing relation with the annular sealing surface and maintains effective sealing even when dimensional changes to the sealing surface occur due to temperature or pressure changes.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to annular metal-to-metalseals for establishing pressure tight sealing engagement with one ormore annular metal components. The present invention is particularlyapplicable for use when tubular elements are positioned end-to-end in amanner defining a joint therebetween, with the metal-to-metal sealassembly having an elastic component providing a joint seal having asubstantially constant radial sealing force. More particularly, thepresent invention concerns an annular sealing assembly permitting theuse of a high strength seal carrier body to which is retained an annularseal insert composed of soft, corrosion resistant metal which issufficiently deformable by seal activating force of the seal carrierbody to conform to the surface geometry and finish of a sealing surfaceand thus establish an efficient high pressure seal therewith.

[0003] 2. Description of the Prior Art

[0004] A metal-to-metal seal is described as follows in U.S. Pat. No.4,471,965, commonly assigned herewith: A metal-to-metal sealing systemincluding an annular metallic seal element having a sealing lip with asealing face of round or curved, as distinguished from annular or flat,cross-sectional configuration, and a cylindrical metallic surfaceagainst which the sealing lip presses in a fluid-tight relationship. Thecylindrical surface has a lead-in chamber on at least one end tofacilitate installation of the seal element into an interference fitagainst the cylindrical surface, and that surface has sufficient axiallength to accommodate relative longitudinal movement between it and thesealing lip as these metallic elements expand and contract in responseto changes in temperature. Thus under normal operating conditions suchas those existing at times other than during a fire, the seal systemfunctions as a pre-load metal-to-metal seal, and when subjected to afire or other greatly elevated temperature the interference fit assuresthat a fluid-tight seal is maintained even though significantlongitudinal or radial movement between the sealing lip and thecylindrical surface occurs. Furthermore, during cool down from hightemperatures the integrity of the seal remains intact. The result is aneffective and reliable metal-to-metal sealing system which providesfluid-tight pressure control over a very wide temperature range, forexample for 1200° F. to minus 75° F., and which can be satisfactorilyemployed in wellhead equipment as well as other applications wherevarying temperatures and/or pressures may be encountered.

[0005] Current rigid metal sealing technology, such as Straight BoreMetal Seals (SBMS), and FX Bonnet gaskets, and RX, BX and AX gasketsrequire higher strength alloys to provide structural integrity andsealing force. These types of seals are widely used in gate valvebonnets, surface and subsea connectors, flowbores and generallythroughout wellhead equipment. The strength requirements of these alloyscan be up to 120,000 psi yield. These seals work by plasticallydeforming a small area into a smooth opposing surface. The seal contactarea is generally small, and these seals are generally (with a fewexceptions), not reusable. Often, due to corrosion requirement, highstrength nickel alloys are selected for these seals. These seals may besensitive to surface finish, installation damage and galling.

OBJECTS OF THE INVENTION

[0006] A primary object of this invention is to provide a highperformance and low cost metal-to-metal sealing assembly for use in highpressure seal applications including straight bore metal seal (SBMS) ofthe nature set forth in U.S. Pat. No. 4,471,965 and further capable ofbeing employed as rough casing metal seals (RCMS), FX bonnet gaskets,RX, BX, AX and other currently used metal-to-metal seal designs.

SUMMARY OF THE INVENTION

[0007] A novel concept for high-pressure, metal-to-metal sealing whichemploys a high strength metal seal body or carrier which facilitatesapplication of spring energy or preload force to a soft metal insertcarried by the seal body to accomplish high pressure metal-to-metalsealing even under conditions of poor surface finish or irregularsealing surface geometry. The present invention has application to rigidmetal-to-metal seal technology including Straight Bore Metal Seals, FXBonnet Gasket Seals, RX, BX, AX gaskets and others. The presentinvention represents an improvement to the High Pressure Fire ResistantSeal set forth in U.S. Pat. No. 4,471,965. The concept of the inventioninvolves separating the structural element (body) from the sealingelement (soft metal circumferential insert). Seal designs using thistechnology employ one or more soft metal inserts that are installed bypressing, shrinking or other retention mechanisms on a higher strengthseal body or carrier. The higher strength seal body elastically deformsand provides a spring energy characteristic to activate the seal,plastically deforming the soft metal circumferential seal insert wheninstalled. The high strength seal body also confines and protects thesoft metal circumferential sealing element against pressure andmechanical abuse. This type of seal increases contact area, allows loweralloy materials (such as 410 stainless steel, 8630, or 4130 steel) to beused for the body of the seal, prevents galling, and also allows thesoft metal seal inserts to be replaced, thus enabling reuse of sealbodies. The soft metal circumferential insert will also allow widermachining tolerances, and seal against surfaces that have defects, suchas scratches. This seal design may also be tolerant to slightly ovalshaped seal bores. The sealing concept of the present inventionrepresents an improvement over metal seals that simply have a softcoating on the surface or require the soft metal to be welded to thehigh strength component. Coatings have limited wear/corrosion life andcannot fill large defects in the sealing area. Welding the soft metal tothe high strength component adds complexity, expense, and limitsmaterial selection and may preclude reuse of the seal.

[0008] Current high pressure metal sealing technology, such as StraightBore Metals Seals (SBMS, described in U.S. Pat. No. 4,471,965), RoughCasing Metal Seals, FX Bonnet gaskets, RX, BX and AX seals requirehigher strength alloys to provide sealing force and structuralintegrity. These types of seals are widely used in gate valve bonnets,surface and subsea connectors, flow bores and generally throughout awide range of wellhead equipment for the petroleum industry. Thestrength requirements of these alloys can be up to 120,000 psi yield.These seals function by plastically deforming a small annular area of aseal element or projection into a smooth opposing annular sealingsurface. The seal contact area is generally small, and these seals aregenerally (with a few exceptions), not reusable. Often, due to corrosionrequirements, high strength corrosion resistant alloys (CRAS) areselected for these seals, thus causing the seals to be of considerableexpense. Especially if the seals can only be installed once and thendiscarded, the impact of seals cost is significant. Using higherstrength body of a less expensive material, with a soft metal insertmade from a more corrosion resistant material, will improve performanceand reduce costs in metal-to-metal sealing. In addition to beingreusable, the soft metal insert will allow interacting seal componentsto have wider machining tolerances, enabling sealing against sealingsurfaces that have defects, such as scratches or poor finish. Currentlytechnology requires that the sealing surfaces be of 32 microinch RMSquality or better. The soft metal seal inserts of the present inventionwill function efficiently even when the surface finish of the sealingsurfaces is of less than that being typically required at the presenttime.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features,advantages and objects of the present invention are attained and can beunderstood in detail, a more particular description of the invention,briefly summarized above, may be had by reference to the preferredembodiment thereof which is illustrated in the appended drawings, whichdrawings are incorporated as a part hereof.

[0010] It is to be noted however, that the appended drawings illustrateonly a typical embodiment of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

[0011] In the Drawings:

[0012]FIG. 1 is a fragmentary vertical section of a wellhead assemblyfor an oil or gas well, showing a number of uses of a metal-to-metalsealing system embodying the principles of the present invention;

[0013]FIG. 2 is a fragmentary section, on an enlarged scale, of ametal-to-metal sealing system according to the present inventionemployed to provide a metal-to-metal seal between a valve bonnet and avalve body, or between two line flanges or other flanged annularelements;

[0014]FIG. 3 is an enlarged fragmentary section of a metal-to metal sealaccording to the present invention between two pipes interconnected byan external pipe coupling;

[0015]FIG. 4 is a sectional view of an annular seal body embodying theprinciples of the present invention;

[0016]FIG. 5 is a fragmentary sectional view of an end portion of theannular seal body of FIG. 4 showing an annular seal groove formed in anannular sealing projection or lip thereof and further showing a softmetal sealing element located within the annular seal groove;

[0017]FIG. 6 is a partial sectional view of an annular seal body havinga soft metal sealing insert located in annular end grooves thereof andrepresenting an alternative embodiment of the present invention;

[0018]FIG. 7 is a sectional view of an annular sealing assemblyrepresenting an embodiment of the present invention and having fourannular sealing lips, each being provided with an annular soft metalsealing insert;

[0019]FIG. 8 is a partial sectional view of an annular seal body havinga soft metal sealing insert located in an annular groove of an annularsealing lip having a generally circular or curved cross-sectionalgeometry;

[0020]FIG. 9 is a partial sectional view of an annular seal body havinga soft metal sealing insert located in annular sealing lip having anannular sealing face of substantially planar configuration;

[0021]FIG. 10 is a partial sectional view of an annular flexible highstrength metal seal body having a soft metal sealing insert located inan annular insert recess and being secured in assembly with the annularseal body by a retainer ring;

[0022]FIG. 11 is a partial sectional view of an annular flexible highstrength metal seal body of generally cylindrical internal configurationand having a pair of soft metal sealing inserts located in annularinsert grooves within respective extremities of the annular seal body;

[0023]FIG. 12 is a partial sectional view of an annular flexible highstrength metal seal body defining a plurality of internal annularsealing projections, ridges or bumps each defining an annular insertrecess having an annular soft metal sealing insert retained therein forsealing engagement with a respective annular sealing surface; and

[0024]FIG. 13 is a fragmentary sectional view of a pair of an annularflexible high strength metal seal body having an annular internalsealing projection defining an annular seal recess containing an annularsoft metal sealing insert and with the sealing insert shown in sealingengagement with an annular external sealing surface of a tubular memberdisposed in telescoping relation with the annular metal seal body.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0025] Referring now to the drawings and first to FIGS. 1 and 2, ametal-to-metal sealing system embodying the principles of the presentinvention is shown to be provided for sealing a number of joints of awellhead or conduit assembly. The metal-to-metal sealing systemcomprises an annular metal seal body element shown generally at 10having an annular base portion 12 which defines at least one annularsealing lip 14 projecting radially toward and establishingmetal-to-metal sealing engagement with an annular surface 18 which maybe a tapered surface as shown in FIG. 1 or a cylindrical surface asshown in FIG. 2.

[0026] As is shown in greater detail in FIG. 2, the annular metal sealbody 10 of the metal-to-metal sealing system has an annular soft metalsealing insert 14 a, being supported with an insert groove of theannular sealing lip 14 and defining an annular sealing surface 14 b. Theannular sealing surface 14 b may be of curved cross-sectionalconfiguration, cylindrical cross-sectional configuration or any othersuitable cross-sectional configuration without departing from the spiritand scope of the present invention. As is also shown in FIG. 2, theannular seal body of the metal-to-metal sealing system also defines oneor more flexible annular intermediate portions 16 being integral withand extending from the annular base portion 12 and having the annularsealing lip 14 with its soft metal insert 14 a projecting therefrom. Theflexible annular intermediate portions 16 provide the annular seal bodywith a spring-like characteristic, so that the flexible annularintermediate portions 16 become flexed and thus preloaded duringassembly and thus continuously urge the annular sealing lip with itssoft metal insert against an annular sealing surface to maintaininterference sealing therewith. The annular seal body 10 is adapted tobe disposed in substantially concentric relation with a member 17, suchas a tubular member of a wellhead assembly, which member defines atleast one annular sealing surface 18 against which the annular sealinginsert 14 a is pressed in an interference fit relationship when theannular seal body is in functional position. A lead-in chamfer 20 on thecylindrical metal surface or wall 18 provides a means to install theannular metal seal body 10 into its illustrated functional position andto accomplish flexing and preloading of the annular seal body 10, andparticularly its flexible annular intermediate portions 16 to ensure itsspring-like forcible metal-to-metal sealing engagement with thecylindrical surface 18. The cylindrical surface 18 is designed to havean axial length that is adequate to ensure that the sealing face of thesoft metal insert is always in metal-to-metal sealing contact with theannular surface 18 regardless of relative movement therebetween inresponse to temperature fluctuations or dimensional changes responsiveto pressure. During assembly, the lead-in chamfer reacts with the softmetal seals 14 a and the annular sealing projections to cause preloadingof the intermediate sections 16 so that the intermediate sections becomeflexed for continuous application of spring force to the annular sealinglips 14 to maintain the soft metal sealing inserts of the annularsealing lips in interference sealing with the annular sealing surface 18of the member 17.

[0027] In the embodiment shown in FIG. 2, the annular seal body 10 alsohas a central web portion 22 that extends radially from the base portion12 to fit into relieved areas 24 a and 24 b in the adjacent faces 26 and27 of annular flanges or other such structures, for properly positioningthe annular seal body at the joint between the adjacent faces andensuring its retention in that location. As shown in FIG. 1, the flangesor other structures defining the adjacent faces 26 and 27 can becomponents of a casing head 30, a tubing head 32, a block valve 34,annulus outlets 36 or to a wide variety of other structures wheremetal-to-metal sealing with internal or external annular surfaces isdesired.

[0028] As further indicated in FIG. 1, the metal-to-metal sealing systemof the present invention also can be utilized in a wellhead as (1) anannulus seal 40 between a mandrel casing hanger 42 and the tubing head32, (2) a bushing seal 44 between an annular hanger bushing 46 and thetubing head 32, (3) an annulus seal 48 for tubing hanger couplings 50 ina dual tubing string completion system and (4) an extended neck hangerseal as shown at 52.

[0029] Since the annular sealing face of the soft metal insert of theannular sealing lip is relatively narrow, and may be of roundedcross-sectional configuration and is significantly softer than thecylindrical sealing surface, i.e., from about ⅕^(th) to about ⅓^(rd) theyield stress of the elastic component of the seal, it will not causedamage to the cylindrical sealing surface against which it is pressedwhen the annular sealing body is in functional position with respect tothe cylindrical sealing surface. This small dimensioned sealing facealso permits minor axial misalignment between the sealing element andcooperative cylindrical surface, such as for example between a tubinghanger and the adapter element, to be accommodated.

[0030] Tests on wellhead equipment utilizing a metal-to-metal sealingsystem having a soft metal sealing insert, according to the teachings ofthe present invention, have shown that the surface finish at the area ofcontact between the seal element and the cylindrical surface can be asrough as 125 micro-inches R.M.S., without jeopardizing the fluidtightness of the seal. This advantage contrasts significantly with thehighly polished surfaces required in some other metal-to-metal sealingsystems, and provides cost reduction opportunities in the manufacturingprocess. A seal that is an example of the described design passed APIPR2, and FMC 500 cycle endurance testing. Testing was done at 5000 psibetween −75° F. and 450° F.

[0031] Additional advantages provided by the present invention include(1) the fact that the cylindrical configuration of the surface againstwhich the sealing surface of the soft metal sealing element is pressedis substantially easier to manufacture than surfaces of otherconfigurations, such as conical, heretofore employed in other metal-tometal sealing systems, and (2) no special bolting or clampingarrangements are necessary.

[0032]FIG. 3 illustrates a dual metal-to-metal seal system according tothe teachings of the present invention, wherein an annular metal sealingelement, shown generally at 60, is provided with two axially spacedouter circumferential annular sealing lips 60 a and 60 b being integraltherewith and projecting radially outwardly therefrom. The sealing lips60 a and 60 b are provided for metal-to-metal sealing engagement withannular inwardly facing annular sealing surfaces 62 and 64 of pipe ends66 and 68 that are secured in assembly by an internally threaded pipecoupling 70. The internal end surfaces 62 and 64 of the pipe ends are ofcylindrical configuration and are intersected by annular internalchamfered surfaces 72 and 74 which serve as lead-in chamfers duringinstallation of the annular metal sealing element 60. The annularsealing lips 60 a and 60 b each define annular seal insert recessesreceiving annular soft metal sealing inserts 76 and 78 which projectfrom the respective seal insert recesses for sealing contact with therespective annular sealing surfaces 62 and 64. The annular metal sealingbody 60, as shown in cross-section in FIG. 3, tapers from a relativelythick and substantially rigid generally cylindrical center section 80 torespective annular end sections 81 and 82 thereof so as to defineflexible intermediate sections 84 and 86. The flexible intermediatesections are flexed radially inwardly as, during assembly, the annularsealing lips 60 a an 60 b and the soft metal inserts 76 and 78 traversethe chamfered surfaces 72 and 74 in progress to the cylindrical sealingsurfaces 62 and 64. The force of assembly being applied to the flexibleintermediate sections 84 and 86 of the annular seal body 60 causesradial flexing of the intermediate sections and thus causes the flexibleintermediate sections to become spring loaded or preloaded. This featureenables the annular sealing lips and their soft metal inserts 76 and 78to maintain interference sealing with the annular sealing surfaces 62and 64 even though the respective pipe ends may change in dimension dueto temperature changes, pressure changes, etc. Thus, the seal 60 employsa high strength, elastically deformable metal body to provide energizingforce, and soft metal sealing inserts to provide the sealing mechanism.The soft metal of the annular sealing inserts allows for much highersealing interference, and also permits effective sealing on a sealing orseating pocket surface that might have surface defects due to poorquality machining or surface damage.

[0033] Referring now to FIGS. 4 and 5, an annular sealing elementembodying the principles of the present invention and being showngenerally at 90, defines an annular body section 92 of generallycylindrical outer peripheral configuration and having integralintermediate flexible sections 94 and 96 integral therewith. Theintermediate body sections have annular sealing lips 98 and 100projecting radially outwardly therefrom and each sealing lip defining anannular seal insert groove. Annular soft metal sealing elements 102 and104 are located within the respective annular seal insert grooves andproject radially outwardly beyond the respective annular sealing lips 98and 100 for sealing contact with respective annular sealing surfaces 106and 108 of tubular elements 110 and 112. The annular seal body 92 isfurther provided with an annular outer peripheral web 114 which isreceived within an annular seal locating recess 116 that iscooperatively defined by the abutting ends of the tubular elements. Theintermediate sections 94 and 96 are rendered more flexible as comparedwith the central section 92 by virtue of tapered end surfaces 118 and120, thus permitting flexing and spring loading of the flexibleintermediate sections by reaction with the internal surfaces of thetubular elements during assembly.

[0034]FIG. 6 illustrates a smooth bore metal seal shown generally at 122having an annular seal body 124 defining a generally cylindrical centersection 126 and having an annular seal locating web 128. The outerperiphery of the annular seal body 124 is tapered from the central bodysection to the respective ends thereof as shown at 130 and 132, thusdefining flexible intermediate sections 134 and 136. The respectiveaxial ends of the annular seal body 122 each define annular sealing lips138 and 140, each in the form of an annular sealing lip or projectionhaving an annular sealing insert groove therein. Annular soft metalsealing inserts 142 and 144 are located within the respective annularseal insert grooves and project from the grooves, with an annularsealing portion thereof disposed for sealing engagement with an annularsealing surface of a tubular element or an annular sealing surface forwhich sealing is desired. The annular sealing lips 138 and 140 may havea curved or rounded cross-sectional configuration as shown, or in thealternative may define a more flattened annular surface in which theannular seat insert element is received. The annular sealing lips mayalso have any other suitable geometry, such as generally elliptical,generally triangular or rectangular if desired and the annular sealgroove may have any suitable cross-sectional configuration, includinggenerally rectangular as shown in FIG. 5, dove tailed or other undercutconfiguration to provide for retention of the annular soft metal sealingelements.

[0035]FIG. 7 illustrates an annular sealing element shown generally at150 which may be referred to as an “H” seal and which is useful forsealing with an internal cylindrical element 152 which is disposed insubstantially concentric, spaced relation within abutting tubularmembers 154 and 156. Though not necessary, the tubular members are shownto have tapered connection flanges 158 and 160 that are retained inassembly by a clamp ring 162. The annular sealing element 150 defines acentral web 164 to which is integrally connected a pair of annular sealbody members 166 and 168. The annular seal body member 166 is ofgenerally cylindrical configuration and defines annular sealing lips 170and 172 at respective axial ends thereof. The annular sealing lips eachdefine annular seal retention grooves having annular soft metal sealingelements 174 and 176 located therein for interference sealing with theouter cylindrical surface 178 of the internal cylindrical element 152.Likewise, the annular seal body member 168 is also of generallycylindrical configuration and defines annular sealing lips 180 and 182each having annular seal retainer grooves defined therein and havingannular soft metal seals 184 and 186 located within the respective sealgrooves, with annular portions thereof projecting from the seal groovesand disposed in interference sealing engagement with the internalannular surfaces 188 and 190 of the pipe ends 154 and 156. An annularpositioning web 192 projects radially from the central portion of theannular seal body member 168 and, in operative position, is locatedwithin an annular seal location recess that is cooperatively defined bythe joint geometry of the abutting pipe ends 154 and 156.

[0036] The annular seal body members 166 and 168 are sufficientlyflexible that they yield or flex typically during assembly of theannular seal 150 with the tubular member 152 and the pipe ends 154 and156. Thus, when in sealing assembly, the annular seal body members applycontinuous spring force to maintain the annular soft metal seal elementsin interference sealing engagement with the respective annular surfaces.This feature enables the seal to maintain its effective sealingcapability even though the annular members change in dimension due totemperature or pressure fluctuations. Also, the soft metal seal memberswill be deformed by the spring force and the force of assembly and willessentially fill surface imperfections of the cylindrical surfaces andachieve effective sealing. The soft metal seal members will alsoaccommodate situations where the annular members are not of perfectlycircular configuration since the soft metal seals will yield toaccommodate such sealing surface irregularities.

[0037] In the partial sectional view of FIG. 8, an annular seal body 192is provided with an annular sealing lip 194 which is of rounded orsemi-circular cross-sectional configuration and projects radially fromthe annular seal body for sealing engagement with a cylindrical sealingsurface, not shown. An annular soft metal seal member 196 is locatedwithin an annular seal retainer groove defined by the annular sealinglip and projects therefrom for interference sealing engagement with thecylindrical sealing surface.

[0038] In the partial sectional view of FIG. 9, an annular seal body 198having a flexible tapered end section 200 defined by a chamfered surface202. At the axial end of the tapered flexible end section is located anannular sealing lip 204 which projects radially from the annular sealbody in a direction toward an annular surface. The annular sealing lip204 is of generally rectangular cross-sectional configuration anddefines a generally cylindrical or slightly curved outer peripheralsurface 206. The annular sealing lip also defines an annular sealretention groove within which is located an annular soft metal sealinsert 208. The annular seal retention groove may be of generallyrectangular cross-sectional configuration as shown or may be of undercutcross-sectional configuration without departing from the spirit andscope of the present invention.

[0039] It should be borne in mind that the cross section of the softmetal insert for each of the embodiments of the invention set forthherein can be circular, elliptical, triangular, rectangular, or ofpolygonal and the seal grooves therefor may be of corresponding ordiffering cross-sectional configuration as desired. The soft metalsealing insert can be used on the sealing radii of Rough Casing MetalSeals, Externally Energized Metal Seals, Straight Bore Metal Seals (suchas described in U.S. Pat. No. 4,471,965). Valve seats may be replacedwith soft metal sealing inserts to minimize machining costs. Soft metalsealing inserts may also be used for ball valve seats, with no need tomatch lap the valve seat and ball to accomplish effective sealing. Thesealing system of the present invention can be used for sealing oninternal or external diameters with equal success. Also, seal designscan use multiple inserts (to increase contact area), or a single inserthaving a broad sealing surface. Existing seal designs can be modifiedefficiently and at low cost to accommodate the soft insert. Radial bumpsof conventional metal-to-metal seals can be flattened and a grove addedto simply fabrication of sealing components having soft metal sealinginserts.

[0040] The partial sectional view of FIG. 10 illustrates an annular sealbody structure 210 having at least one tapered flexible end section 212which is defined by a chamfered surface 214 such as discussed above. Theaxial end or ends of the annular seal body define an annular seal recess216 within which is located an annular soft metal seal element 218. Aretainer ring 220, such as a snap ring, is received by the axial end ofthe annular seal body and serves to retain the soft metal sealingelement 218 within the seal recess or groove. Thus, the annular softmetal seal is readily replaceable, so that the annular seal body can bereused even under circumstances where the annular soft metal seal mighthave become damaged during assembly, disassembly or during use.

[0041] Referring now to FIG. 11, the partial sectional view illustratesan annular seal body shown generally at 222, having a central bodysection 224 and intermediate body sections 226 and 228. Flexible axialend sections 230 and 232 of the annular seal body 222 are defined byannular chamfered surfaces 234 and 236. These flexible end sections areprovided with annular seal retention grooves having soft metal sealingelements 238 and 240 retained therein. The soft metal sealing elementseach define annular portions thereof which project radially beyond theannular surface 242 and establish interference sealing with an annularmember. The annular surface 242 may be of cylindrical configuration andmay extend completely to the axial ends of the annular seal body 222 asshown. In this case, the only portions of the seal assembly projectingradially beyond the cylindrical surface 242, except for an annularlocator web 244, the purpose of which is explained above, are thesealing lips and portions of the soft metal sealing elements 238 and240. During assembly of the annular seal body with annular surfaces,such as abutting pipe sections, the chamfered flexible axial ends of theannular seal body can be flexed by chamfered lead-in surfaces in themanner discussed above, to provide the annular seal body with preloadedspring-like characteristics upon assembly for continuous application ofradially directed force to the annular soft metal seals to maintain themin interference sealing with the respective annular sealing surfacescontacted by the soft metal seals.

[0042]FIG. 12 indicates that an annular sealing member shown generallyat 250, embodying the principles of the present invention, may beprovided with more than one or two annular soft metal sealing elements.The annular sealing member is defined by an annular seal body member 252having a central body section 254 which defines circular sealingprojections or lips 256 and 258 each defining an annular seal retainergroove having an annular soft metal seal element 260 and 262 locatedtherein. The annular seal body is provided with flexible axial ends 264and 266 which are defined by chamfered surfaces 268 and 270. Theseflexible axial ends also define annular projections or sealing lips 272and 274 which have annular seal retention grooves containing annularsoft metal seal members 276 and 278. Typically, the plurality of metalseal inserts of the annular sealing member 250 have the same internal orexternal dimension, so that multiple seals can be established on acylindrical surface to enhance the sealing capability of the annularsealing unit. If desired, however, the intermediate seals and the axialend seals or each of the seal inserts may be of differing dimensionaccording to the geometry of the surface or surfaces to be sealed. Theannular seal member 250 is especially adaptable for use as a StraightBore Metal Seal, with the plurality of annular soft metal seal inserts,thus enhancing the surface contact that is ordinarily possible whenseals are used having only one or two soft metal seal inserts.

[0043] As shown in FIG. 13, sealing according to the teachings of thepresent invention may be accomplished between telescopically arrangedtubular elements. A tubular element 280 having a cylindrical externalsurface 282 is shown to be telescopically received within a tubularmember 284. To accomplish sealing, the outer tubular member defines aninternal annular sealing projection or lip 286 having an annular sealretention groove 288. An annular soft metal seal is retained within theannular seal retention groove, with an annular portion thereofprojecting radially beyond the annular sealing projection 286 and thusdisposed for sealing engagement with the outer cylindrical surface 282of the tubular element 280. It should be borne in mind that the annularsealing lip may, in the alternative, be located at the outer peripheryof the inner tubular element, causing the soft metal seal to bepositioned for sealing engagement with the inner cylindrical surface ofan outer tubular member.

[0044] In view of the foregoing it is evident that the present inventionis one well adapted to attain all of the objects and featureshereinabove set forth, together with other objects and features whichare inherent in the apparatus disclosed herein.

[0045] As will be readily apparent to those skilled in the art, thepresent invention may easily be produced in other specific forms withoutdeparting from its spirit or essential characteristics. The presentembodiment is, therefore, to be considered as merely illustrative andnot restrictive, the scope of the invention being indicated by theclaims rather than the foregoing description, and all changes which comewithin the meaning and range of equivalence of the claims are thereforeintended to be embraced therein.

We claim:
 1. An annular metal-to-metal sealing system, comprising: ametal member defining an annular sealing surface; an annular seal bodycomposed of high strength metal material being positioned insubstantially concentric relation with said annular sealing surface; andat least one annular soft metal sealing insert being supported by saidannular seal body and being maintained in sealing engagement with saidannular sealing surface by said annular seal body.
 2. The annularmetal-to-metal sealing system of claim 1, comprising: said annular sealbody being flexible and having spring characteristics and applyingspring energy to said circumferential soft metal sealing insert forenergizing sealing engagement thereof with said annular sealing surface.3. The annular metal-to-metal sealing system of claim 1, comprising: acircumferential sealing lip being defined by said annular seal body andhaving an annular seal recess therein; and said soft metal seal beinglocated within said annular seal recess, with an annular portion thereofprojecting from said annular seal recess and having sealing engagementwith said annular sealing surface.
 4. The annular metal-to-metal sealingsystem of claim 3, comprising: said annular seal recess being defined byan undercut groove of non-circular cross-sectional configuration; andsaid annular soft metal sealing insert having a cross-sectionalconfiguration substantially conforming to said non-circularcross-sectional configuration and having an annular sealing portionthereof projecting from said undercut groove for metal-to-metal sealingengagement with said annular sealing surface.
 5. The annularmetal-to-metal sealing system of claim 1, comprising: said annular sealbody being flexible and having spring characteristics and applyingspring force to said circumferential soft metal sealing insert forenergizing sealing engagement thereof with said annular sealing surface;and said circumferential soft metal insert being plastically deformableby said spring force of said annular seal body to establish sealingengagement with surface irregularities of said annular sealing surface.6. The annular metal-to-metal sealing system of claim 1, comprising:said annular seal body having an elastic characteristic and becomingflexed during assembly with said annular sealing surface andestablishing a spring force applying substantially constant radialsealing force to said annular soft metal seal for maintaining sealingthereof with said annular sealing surface.
 7. The annular metal-to-metalsealing system of claim 6, comprising: said annular soft metal insertbeing sufficiently elastically deformable by said spring force toestablish metal-to-metal interference sealing engagement thereof withsaid annular sealing surface.
 8. The annular metal-to-metal sealingsystem of claim 1, comprising: said at least one soft metal insert beingremovable and replaceable with respect to said annular seal body.
 9. Theannular metal-to-metal sealing system of claim 1, comprising: saidannular seal body defining at least one annular seal recess; and said atleast one soft metal insert being received within said annular sealrecess with an annular portion thereof projecting from said annular sealrecess for sealing engagement with said annular sealing surface.
 10. Theannular metal-to-metal sealing system of claim 9, comprising: a sealretainer member being in removable assembly with said annular seal bodyand retaining said at least one soft metal seal in removable assemblywithin said annular seal recess.
 11. The annular metal-to-metal sealingsystem of claim 1, comprising: said annular seal body being of elasticcharacter capable of being flexed and upon flexing becoming springloaded for substantially continuous application of spring force urgingsaid annular soft metal insert against said annular sealing surface withsufficient force to establish interference sealing therewith, saidspring force maintaining said annular soft metal insert in sealingengagement with said annular sealing surface during changes of dimensionof said annular sealing surface.
 12. The annular metal-to-metal sealingsystem of claim 11, comprising: said at least one annular soft metalinsert being composed of corrosion resistant metal material.
 13. Theannular metal-to-metal sealing system of claim 11, comprising: saidannular soft metal insert being plastically deformable against saidannular sealing surface by said spring force and establishing asufficiently broad sealing area for metal-to-metal interference sealingwith said annular sealing surface.
 14. The annular metal-to-metalsealing system of claim 1, comprising: said annular sealing surfacebeing a pair of annular sealing surfaces disposed in substantiallyconcentric spaced relation and defining an annulus therebetween; saidannular seal body substantially bridging said annulus and having atleast a pair of annular seal recesses facing respective annular sealingsurfaces; and at least a pair of annular soft metal sealing insertsbeing located within respective annular seal recesses with annularportions thereof having metal-to-metal interference sealing engagementwith respective annular sealing surfaces.
 15. The annular metal-to-metalsealing system of claim 1, comprising: said annular soft metal insertbeing composed of corrosion resistant metal alloy having from ⅕ to ⅓ ofthe yield stress of said metal member.
 16. The annular metal-to-metalsealing system of claim 1, comprising: said annular soft metal insertbeing composed of a soft metal material being compatible withenvironmental conditions to which said annular soft metal insert issubjected.
 17. The annular metal-to-metal sealing system of claim 1,comprising: said annular soft metal insert having an effective sealingtemperature range of from about −80° F. to about 450° F.
 18. The annularmetal-to-metal sealing system of claim 1, comprising: said metal memberbeing a pair of metal members having a pair of radially spacedsubstantially concentric metal sealing surfaces; and said annular sealbody supporting at least a pair of annular soft metal inserts forrespective metal-to-metal sealing with said radially spacedsubstantially concentric metal sealing surfaces.
 19. The annularmetal-to-metal sealing system of claim 18, comprising: said annular sealbody having an X-shaped configuration defining two inner annular sealingmembers and two outer annular sealing members; and annular soft metalsealing inserts being supported by each of said inner and outer annularsealing members and being oriented for sealing with radially spacedsubstantially concentric annular sealing surfaces.
 20. The annularmetal-to-metal sealing system of claim 19, comprising: said two innerannular sealing members and two outer annular sealing members eachdefining annular seal support grooves; and said annular soft metalsealing inserts being supported within respective annular seal supportgrooves with portions thereof exposed for metal-to-metal sealing withrespective annular sealing surfaces.
 21. The annular metal-to-metalsealing system of claim 18, comprising: said annular seal body having anH-shaped configuration defining two inner annular sealing members andtwo outer annular sealing members; and annular soft metal sealinginserts being supported by each of said inner and outer annular sealingmembers and being oriented for sealing with radially spacedsubstantially concentric annular sealing surfaces.
 22. An annularmetal-to-metal sealing system, comprising: at least one metal memberdefining at least one annular sealing surface; an annular seal bodycomposed of high strength flexible metal material having springcharacteristics and having at least an annular portion thereofpositioned in substantially concentric relation with said at least oneannular sealing surface and having at least one annular seal retainergroove; and at least one annular soft metal sealing insert beingsupported at within said at least one seal retainer groove of saidannular seal body and having an annular portion thereof exposed fromsaid at least one annular seal retainer groove and maintained inmetal-to-metal sealing engagement with said annular sealing surface bysaid spring characteristics of said annular seal body.
 23. The annularmetal-to-metal sealing system of claim 22, comprising: said annular sealbody being elastically deformed upon being placed in sealing assemblywith said at least one metal member and developing a spring force; atleast one circumferential sealing lip being defined by said annular sealbody and having an annular seal recess therein; said soft metal sealinginsert being located within said annular seal recess, with an annularportion thereof projecting from said annular seal recess and havingsealing engagement with said annular sealing surface; and saidcircumferential soft metal insert being plastically deformable by saidspring force of said annular seal body to establish sealing engagementwith surface irregularities of said annular sealing surface of saidannular metal member and to accommodate dimensional changes of saidannular sealing surface by heat or pressure.
 24. The annularmetal-to-metal sealing system of claim 22, comprising: a seal retainermember being in removable assembly with said annular seal body andretaining said at least one soft metal seal in removable assembly withinsaid annular seal recess.
 25. The annular metal-to-metal sealing systemof claim 22, comprising: said annular seal body being of elasticcharacter capable of being flexed and upon flexing becoming springloaded for substantially continuous application of spring force urgingsaid annular soft metal insert against said annular sealing surface withsufficient force to deform said annular soft metal sealing insert andform a broad annular sealing surface thereon to establish metal-to-metalinterference sealing with said annular sealing surface, said springforce maintaining said annular soft metal insert in sealing engagementwith said annular sealing surface upon changes of dimension of saidannular sealing surface.
 26. The annular metal-to-metal sealing systemof claim 22, comprising: said at least one annular sealing surface beinga pair of annular sealing surfaces disposed in substantially concentricspaced relation and defining an annulus therebetween; said annular sealbody substantially bridging said annulus and having at least a pair ofannular seal recesses facing respective annular sealing surfaces; and atleast a pair of annular soft metal inserts being located withinrespective annular seal recesses with annular portions thereof havinginterference sealing engagement with respective annular sealingsurfaces.
 27. In a wellhead assembly for an oil, gas well, geothermal,or water injection, a fire-resistant metal-to-metal fluid seal systemfor isolating fluids subjected to cyclic variations in temperatureand/or pressure, said system comprising: a. a pipe suspension elementwith an end portion functional as an annular metal seal element having(1) a base, (2) a sealing member defining a seal retaining groove; (3) asoft metal sealing insert being disposed within said seal retaininggroove and defining a sealing lip with a sealing face of curvedcross-sectional configuration, and (4) an intermediate lip-supportingportion extending between the base and the sealing lip; and b. awellhead element surrounding said pipe suspension element and having ametallic cylindrical surface against which said sealing lip of said softmetal sealing insert presses in an interference fit relationship whichin functional position therewith, said cylindrical surface having anaxial dimension sufficient to assure continuous contact thereof withsaid sealing lip regardless of the magnitude of expansion andcontraction experienced by the seal system in response to temperatureand/or pressure fluctuations.
 28. A wellhead assembly according to claim27 wherein the sealing member has at least one sealing lip defining saidseal retaining groove.
 29. A wellhead assembly according to claim 28wherein the wellhead element includes a frusto-conical surfaceintersecting the metallic cylindrical surface, said frusto-conicalsurface functioning as a lead-in chamfer for installation of said sealelement.
 30. A metal-to-metal seal system according to claim 27 whereinthe seal element has a plurality of sealing lips each having a sealgroove and each seal groove having a soft metal sealing member thereinand disposed for metal-to-metal sealing engagement with said metallicsealing surface.
 31. A metal-to-metal seal system according to claim 30wherein the seal element has two sealing lips each having a seal grooveand each seal groove having a soft metal sealing member therein disposedfor establishing a fluid-tight seal with two separate cylindricalsurfaces.
 32. A metal-to-metal seal system according to claim 31 whereinthe seal element includes a web portion intermediate the soft metalsealing inserts of the two sealing lips to locate and retain said sealelement in functional position with respect to the cylindrical surfaces.33. A metal-to-metal seal system according to claim 30 wherein the sealelement has a generally U-shaped cross-sectional configuration, andinner and outer sealing lips each having seal grooves therein and havingsoft metal sealing inserts within said seal grooves for establishing afluid seal in the annulus between two concentric cylindrical surfaces.34. A metal-to-metal seal system according to claim 30 wherein the sealelement has a generally step-shaped cross-sectional configuration, andinner and outer sealing lips each having a seal groove and each sealgroove having a soft metal sealing insert therein disposed to provide afluid seal between two coaxial cylindrical surfaces.
 35. Ametal-to-metal seal system according to claim 30 wherein the sealelement has a generally H-shaped cross-sectional configuration, and atleast three sealing lips each having a seal groove therein and each sealgroove having a soft metal insert therein disposed to provide a fluidseal with at least three separate cylindrical surfaces.
 36. Ametal-to-metal seal system according to claim 35 wherein the sealelement has four sealing lips and each seal groove having a soft metalsealing insert therein, two of said soft metal sealing inserts disposedto sealing engage one or more outer cylindrical surfaces surroundingsaid seal element, and two of said soft metal sealing inserts disposedfor sealing engagement with one or more inner cylindrical surfacessurrounded by said seal element.
 37. A metal-to-metal seal systemaccording to claim 36 wherein the seal element further includes a webportion to locate and retain said seal element in proper functionalposition for positioning said soft metal sealing inserts inmetal-to-metal sealing engagement with said inner cylindrical surfaces.